The source code consists of roughly half a million lines of code*. What you copied here is just a bunch of type and macro declarations for palettes and later some code to load palettes - two very small and pretty unimportant pieces of code. Sorry, nobody is going to "translate [all of it] to English". If you want to tinker with the source code, you won't be able to avoid learning C.

[*] Which is unnecessarily bloated. One part of the effort to improve maintainability in JA2-Stracciatella is to simplify the source code, which resulted in about 150.000 lines (short: 150 kLOC) less code.